Guide rail mechanism for a bonding apparatus

ABSTRACT

A guide rail mechanism for a bonding apparatus for transferring a workpiece such as a lead frame, etc. including a pair of guide rails each comprising an edge surface guide rail element for guiding the edge surface of the workpiece and an undersurface guide rail element disposed beneath the edge surface guide rail element so as to support the undersurface of the edge portion of the workpiece. A driver for the undersurface guide rail element comprised of a rotational shaft with an eccentric cam portion and other parts is installed so as to move the undersurface guide rail element, thus changing the positional relationship between the edge surface guide rail element and the undersurface guide rail element for workpieces of different thicknesses.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a guide rail mechanism for a bondingapparatus.

2. Prior Art

Conventionally, the guide rail mechanisms used in bonding apparatusessuch as die bonding apparatuses and wire bonding apparatuses, etc.include, as shown in FIGS. 9 and 10, a pair of guide rail sections 2Aand 2B which guide both sides of a workpiece such as a lead frame 1.Since these guide rail sections 2A and 2B have more or less the samestructures, the same or corresponding members will be described usingthe same reference numerals.

A pair of width adjustment guides 4 which extend in the direction ofwidth of a lead frame 1 being conveyed are disposed on the upper surfaceof a stand 3, and a slider 5 which is moved by a driving means (notshown) is slidably disposed on each of the width adjustment guides 4.Here, the "direction of width" and "inside" of the lead frame 1 areindicated relative to the direction of the position of the heating block14 (described later) which is located substantially in the centralportion of a guide rail stand 8 (also described later) as shown in FIG.9. A sliding block 6 is provided on the slider 5, and a supporting block7 is fastened to the sliding block 6; in addition, a guide rail stand 8is fastened to the inside surface of the supporting block 7.

A screw shaft 9, which extends vertically upward and is provided with aninternal thread 9a formed in its upper end part, is fastened to each ofthe guide rail stands 8. A rail height adjustment spacer 10, which isinserted into the screw shaft 9, and a frame guide rail 11 are providedon the surface of each guide rail stand 8. Furthermore, a spring 12 ismounted on a portion of the screw shaft 9 on each frame guide rail 11,and a bolt 13 is tightened in the internal thread 9a of the screw shaft9, so that the rail height adjustment spacer 10 and frame guide rail 11are fastened in place by being pressed against the guide rail stand 8 bythe spring 12. Furthermore, a heating block 14 which heats the leadframe 1 is disposed between the frame guide rails 11. This heating block14 is raised and lowered by a driving means (not shown).

Guide rail mechanisms of this type are described in, for example,Japanese Patent Application Laid-Open (Kokai) Nos. S55-26696 andS60-63935 and Japanese Patent Application Publication (Kokoku) No.63-56121.

In the above prior art, the lead frame 1 is fed along the guide sections11a of the frame guide rails 11 to the bonding position by a feedingclaw (not shown). Following positioning, bonding is performed by abonding apparatus (not shown) to the lead frame 1. In a die bondingapparatus, semiconductor pellets are bonded to the surface of the leadframe 1; while in a wire bonding apparatus, wires are connected betweenleads of the lead frame 1 and pads on the semiconductor pellets arebonded to the surface of the lead frame 1.

Thus, in bonding apparatuses, semiconductor pellets are bonded to thesurfaces of lead frames, or wires are connected between the leads ofsuch lead frames and the pads of semiconductor pellets. In this case,the upper surface of the lead frame act as a reference surface at theheight position during bonding. Accordingly, if the thickens of the leadframe changes as a result of a change in the type of workpiece (leadframe, for instance) to be handled, e. g., in cases where the workpieceto be handled is thicker than a previous workpiece that has beenhandled, the height of the upper surface of the lead frame, i. e., theupper surface of the reference surface, is heightened; and as a result,the frame guide rails 11 must be lowered so as to compensate thedifference in thickness, thus keeping the height of the referencesurface at a constant value.

More specifically, it is necessary to change the rail height adjustmentspacers 10 which have a thickness suited to the thickness of the leadframe to be handled. The rail height adjustment spacers 10 are changedas follows: the bolts 13 are loosened and removed from the screw shafts9, the frame guide rails 11 and rail height adjustment spacers 10 areremoved, new rail height adjustment spacers 10 are installed, the railheight adjustment spacers 10 and frame guide rails 11 are put back, andthen the bolts 13 are tightened back in the screw shafts 9.

Especially in cases where the guide sections 11a of the frame guiderails 11 are angled C-shaped ("[") rails and angled reverse-C-shaped("]") rails as shown in FIGS. 9 through 11, it has conventionally beennecessary to replace the frame guide rails 11 entirely if the thicknesst of the lead frame 1 changes greatly. Ordinarily, the thickness t, asseen in FIG. 11, of a lead frame is in the range of 0.1 to 0.4 mm.Accordingly, the height h of the guide sections 11a of the frame guiderails 11 is obtained by adding a clearance c to the thickness t of thelead frame 1 so that lead frame 1 can be conveyed. Consequently, incases where the thickness t of the lead frame 1 is within the height hof the guide sections 11a, it is necessary to replace only the railheight adjustment spacers 10, even if the thickness t of the lead frame1 should vary. However, in cases where the thickness t of the changedlead frame 1 exceeds the height h of the guide sections 11a, the frameguide rails 11 must be replaced with frame guide rails 11 that aresuited to the changed lead frame 1.

In the above prior art, in cases where the thickness t of the lead frame1 changes as a result of a change in the type of workpiece to behandled, it is necessary to loosen and remove the bolts 13, replace therail height adjustment spacers 10, and then put the bolts 13 back andtighten them. In addition, the pair of frame guide rails 11 areinstalled so as to extend in the direction in which the lead frame 1 isconveyed; accordingly, each one of the guide rail sections 2A and 2B isprovided with two screw shafts 9 along the conveying direction of thelead frame 1, and springs 12 are mounted on the respective screw shafts9 so that bolts 13 press the frame guide rails 11 and rail heightadjustment spacers 10 against the guide rail stands 8 via the spring 12.In other words, each of the guide rails 11 have two screw shafts 9, twoscrews 12, two bolts 13, etc. As a result, when a lead frame of adifferent thickness is to be handled, four bolts 13 are loosened andremoved, the rails 11 are adjusted for the lead frame to be handled, andthen the bolts 13 are remounted and re-tightened. Thus, it requires along time for adjustment, resulting in a drop in productivity.

Furthermore, a plurality of rail height adjustment spacers 10 withdifferent thicknesses that match the thickness of the changed lead framemust be prepared so as to be used. This creates problems in terms of thecontrol and storage of the spacers 10; moreover, equipment costs areincreased. In the case of frame guide rails 11 which have guide sections11a of the type shown in FIGS. 9 and 10, a plurality of sets of frameguide rails 11 must be prepared. This causes the equipment cost toincrease.

SUMMARY OF THE INVENTION

Accordingly, the first object of the present invention is to provide aguide rail mechanism for a bonding apparatus in which the adjustment ofthe height of the frame guide rails in response to a change in the type(thickness) of a workpiece to be handled can be performed in a shorttime, improving the productivity.

The second object of the present invention is to provide a guide railmechanism for a bonding apparatus in which the cost of the equipmentrequired for each change in the type of workpiece to be handled can bereduced.

The first and second objects are accomplished by a unique structure fora guide rail mechanism for a bonding apparatus that includes a pair ofguide rails for guiding a workpiece such as a lead frame and the like;and in the present invention each of the guide rails comprises an edgesurface guide rail element, which is installed in a guide rail stand andguides the edge surface of a workpiece, and an undersurface guide railelement, which is disposed beneath the edge surface guide rail elementand supports the undersurface of the edge portion of a workpiece; and inaddition, an undersurface guide rail element driving means is providedso as to raise and lower the undersurface guide rail element.

In the above-described structure, the edge surface guide rail element,which is provided on the guide rail stand and guides the edge surface ofthe workpiece, may be formed so as to open upward.

Furthermore, in the above structure, the undersurface guide rail elementdriving means is comprised of a rotational shaft and a rotationaldriving means, in which the rotational shaft consists of a shaft portionwhich is rotatably disposed on a guide rail stand and a cam portionwhich is provided at the end of the shaft portion and supports, raisesand lowers the undersurface guide rail element; and the rotationaldriving means is, for instance, a motor which rotationally drives therotational shaft.

Such an undersurface guide rail element driving means may furtherinclude a control device that controls the amount of driving of therotational driving means (a motor) or may further include a rotationalshaft positioning means that holds the rotational shaft in a pluralityof stopping positions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially sectional side view of a first embodiment of theguide rail mechanism for a bonding apparatus according to the presentinvention;

FIG. 2 shows the essential portion of FIG. 1, wherein FIG. 2(a) is anenlarged sectional view guiding a lead frame of a large thickness, andFIG. 2(b) is an enlarged sectional view guiding a lead frame of a smallthickness;

FIG. 3 is a view taken in the direction of arrow 3 in FIG. 2(a), showingthe cam portion;

FIG. 4 shows the essential portion of the second embodiment of thepresent invention, wherein FIG. 4(a) is an enlarged sectional viewguiding a lead frame of a large thickness, and FIG. 4(b) is an enlargedsectional view guiding a lead frame of a small thickness;

FIG. 5 is a view taken in the direction of arrow 5 in FIG. 4(a), showingthe cam portion;

FIG. 6 shows the essential portion of the third embodiment of thepresent invention;

FIG. 7 shows the essential portion of the fourth embodiment of thepresent invention;

FIG. 8 shows the essential portion of the fifth embodiment of thepresent invention, showing the cam portion viewed in the same way asshown in FIGS. 3 and 5;

FIG. 9 is a partially sectional side view of a conventional guide railmechanism for a bonding apparatus;

FIG. 10 is an enlarged sectional view of the essential portion in FIG.9; and

FIG. 11 is an explanatory diagram illustrating the relationship betweena lead frame and a guide section of the guide rails.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The first embodiment of the present invention will be described withreference to FIGS. 1 through 3.

As in a conventional mechanism, a pair of width adjustment guides 4which extend in the direction of width of a lead frame 1 being conveyedare disposed on the upper surface of a stand 3, and sliders 5 which aremoved by a driving means (not shown) are slidably disposed on thesewidth adjustment guides 4. A sliding block 6 is fastened to each slider5, a supporting block 17 is fastened to this sliding block 6, and aguide rail stand 18 is provided on the inner surface of this supportingblock 17.

Each of the guide rails 21 of the guide rail sections 20A and 20Bcomprises an edge surface guide rail element 22 which guides the edgesurface of the lead frame 1, and an undersurface guide rail element 23which supports the undersurface of the lead frame 1. The edge surfaceguide rail elements 22 are fastened to the inside surfaces of the guiderail stands 18; and the undersurface guide rail elements 23 are raisedand lowered by an undersurface guide rail element driving means whichraises and lowers the undersurface guide rail element and will bedescribed below.

Rotational shafts 25, each of which comprises a shaft portion 25a and acam portion 25b, are inserted into the guide rail stands 18 at the shaftportions 25a so that the rotational shafts 25 can be rotated. As bestseen in FIG. 3, the cam portion 25b of each of the rotational shafts 25is offset by eccentricity E from the shaft portion 25a. A motor 26 isinstalled on each of the supporting block 17, and the output shaft ofthe motor 26 is coupled to the outside end of each shaft portion 25a.The undersurface guide rail element 23 is placed on the cam portion 25b,and a retaining plate 27 is fastened to the end surface of the camportion 25b by a screw 28. Here, the portion of the undersurface guiderail element 23 that corresponds to and faces the cam portion 25b ofeach rotational shaft 25 is inserted into a space between the edgesurface guide rail element 22 and the retaining plate 27. Furthermore, aspring 29 is provided between the undersurface guide rail element 23 andthe supporting block 7 so that the undersurface guide rail element 23 ispressed against the cam portion 25b by the spring 29.

Next, the operation will be described with reference to FIG. 2. In FIG.2(a), a thick lead frame 1A is conveyed, while in FIG. 2(b) a thin leadframe 1B is conveyed.

When the motors 26 (only one of the two is shown) are driven and therotational shafts 25 are rotated, the height of the upper surfaces 25b'of the cam portions 25b (which are eccentric shafts offset from thecenters of the shaft portions 25a) changes, and the undersurface guiderail elements 23 are raised or lowered, thus changing the distancebetween the edge surface guide rail element 22 and the undersurfaceguide rail elements 23.

Accordingly, when the type of workpiece (lead frame) to be handled ischanged from a thick lead frame 1A shown in FIG. 2(a) to a thin leadframe 1B shown in FIG. 2(b), the motors 26 are driven so that theundersurface guide rail elements 23 are raised by an amount thatcorresponds to the difference in thickness and so that the upper surfaceof the thin lead frame 1B is positioned at the same height level as theupper surface of the thick lead frame 1A. Reversely, when the type ofworkpiece (lead frame) to be handled is changed from a thin lead frame1B shown in FIG. 2(b) to a thick lead frame 1A shown in FIG. 2(a), themotors 26 are driven in reverse so that the undersurface guide railelements 23 are lowered by an amount that corresponds to the differencein thickness and so that the upper surface of the thick lead frame 1A ispositioned at the same height level as the upper surface of the thinlead frame 1B.

Thus, the height of the undersurface guide rail elements 23 are adjustedin accordance with the thickness of the workpiece to be handed merely bydriving the motors 26. Accordingly, the height of the undersurface guiderail elements 23 can be adjusted in a short time, and the productivityis improved.

Such effect can be further enhanced by linking a control device 50 tothe motors 26. In other words, an instant response to the changes in thetype (or thickness) of workpiece to be handled can be accomplished byinputting in advance the relationships of the type of lead frame 1,amount of driving of the motors 26 and stopping positions of the camportions 25b into the control device 50 so that the control devicecontrols the motors 26 accordingly.

In addition, since there is no need in the present invention for railheight adjustment spacers 10 (see FIGS. 9 and 10) used for each type ofworkpiece in the conventional devices, the equipment costs can bereduced.

FIGS. 4 and 5 illustrate a second embodiment of the present invention.Though the rotational shafts 25 are rotated by the motors 26 in thefirst embodiment, the rotational shafts 25 in the second embodiment arerotated by hand. Constituting elements which are the same as in thefirst embodiment of FIGS. 1 through 3 or which correspond to those inFIGS. 1 through 3 are labeled with the same reference numerals, and adescription of such is omitted.

A knob 25c, instead of the motor 26, is disposed on the outside end ofeach one of the rotational shafts 25, and a spring 30 is mounted on theshaft portion 25a of the rotational shaft 25 so that the spring 30 isbetween the guide rail stand 18 and knob 25c. Furthermore, a rotationalshaft positioning means which holds the rotational shaft 25 in aplurality of rotational positions (four positions in the caseillustrated embodiment) is disposed on the rotational shaft 25 and guiderail stand 18. More specifically, four notch holes 25d are formed in theouter surface of the rotational shaft 25, a screw 35 is screwed into theguide rail stand 18 so as to positionally correspond to the notch holes25d, a spring accommodating hole 35a is formed in the lower end of thescrew 35, a spring 36 is installed in the spring accommodating hole 35a,and a ball 37 is provided at the end of the spring 36 so as to face thenotch holes 25d.

Accordingly, in this second embodiment, when the knobs 25c (only one ofthe two is shown) are turned by hand, the rotational shafts 25 arerotated; as a result, the height positions of the upper surfaces of thecam portions 25b are changed so that the undersurface guide railelements 23 are raised or lowered. When, by the spring 36, the ball 37engages one of the notch holes 25d as a result of the turning of theshaft portions 25a of the rotational shafts 25, the rotational shaft 25is held in that position. Thus, by forming four notch holes 25d inpositions corresponding to the positions of the cam portions 25b forfour different types (in thickness) of workpieces, the upper surface ofthe lead frame 1 (thick lead frame 1A of thin lead frame 1B) can beadjusted to a constant height level as in the first embodiment.

In the second embodiment, four notch holes 25d are formed; however,there is no restriction on the number of notch holes 25d formed. It goeswithout saying, though, that the differences in the thickness of theworkpieces or lead frames are limited to the number of notch holes 25d.Furthermore, the positional holding of the rotational shafts 25 is notlimited to the described notch hole and ball combination.

FIGS. 6 and 7 illustrate third and fourth embodiments of the presentinvention. FIG. 6 corresponds to FIG. 2, and FIG. 7 corresponds to FIG.4.

Incidentally, guide rails come in many different types, including railswhich have angled C-shaped ("[") and angled reverse-C-shaped ("]") guidesections and rails which have guide sections whose upper surfaces areopen. For instance, Japanese Patent Application Laid-Open (Kokai) No.S60-63935, Japanese Patent Application Publication (Kokoku) No.S63-56121 and FIGS. 10 and 11 of the present application show railswhich have C-shaped and reverse-C-shaped guide sections; and the railswith guide sections whose upper surfaces are open are shown in JapanesePatent Application Laid-Open (Kokai) No. S55-26696.

The first and second embodiments are described with reference to therails which have angled C-shaped ("[") and angled reverse-C-shaped ("]")guide sections, and protruding sections 22a which extend toward theupper surface of the lead frame 1 are formed on the edge surface guiderail elements 22.

However, in the third and fourth embodiments shown in FIGS. 6 and 7,frame rails 21 in which the upper surfaces of the guide sections areopen are used; and thus these embodiments include no protruding sections22a. As seen from FIGS. 6 and 7, the lead frame 1 contacts the framerails 21 with its end surface(s). The same effect as those describedwith reference to the first and second embodiments is obtained by thethird and fourth embodiments. Thus, it is clear that the presentinvention is applicable to rails which have the open guide sections.

FIG. 8 illustrates the fifth embodiment of the present invention.

Though in the respective embodiments described above the cam portions25b are formed as eccentric shafts, the cam portions 25b of the fifthembodiment is formed with flat external circumferential surfaces 40, 41,42 and 43. The distance of each one of the flat surfaces 40, 41, 42 and43 from the center 44 is set to be different from each other accordingto the type (thickness) of workpiece to be handled. Since these flatsurfaces function as in the same manner as the eccentric shaft, the sameeffect as those described in the first through fourth embodiments isobtained by this fifth embodiment.

In the shown embodiment, four flat surfaces 40, 41, 42 are 43 areprovided in the cam portion 25b; however, there is no restriction on thenumber of flat surfaces. As in the case of FIGS. 4 and 5, it goeswithout saying, though, that differences in the thickness of the leadframes are limited to the number of flat surfaces.

In the embodiments shown in FIGS. 1 through 3 and FIG. 6, the rotationalshafts 25 which have cam portions 25b, and the motors 26, which effectedrotational driving of the rotational shafts 25, form an undersurfaceguide rail element driving means which raises and lowers theundersurface guide rail elements 23. However, it is also possible toinstall the undersurface guide rail elements 23 on the guide rail stands18 so that the undersurface guide rail elements 23 are movable in avertical direction and move the undersurface guide rail elements 23 upand down from below by means of motors, air-cylinders, etc.

As seen from the above, according to the present invention for a guiderail mechanism, each of the frame guide rails comprises an edge surfaceguide rail element, which is fastened to a guide rail stand and guidesthe edge surface of a lead frame, and an undersurface guide railelement, which is provided beneath the edge surface guide rail elementand supports the undersurface of the edge portion of the lead frame; andan undersurface guide rail element driving means is provided so as toraise and lower the undersurface guide rail elements. Accordingly,adjustment of the height of the frame guide rails in accordance withchanges in the type (thickness) of lead frames can be accomplished in ashort time, thus improving the productivity. In addition, the costrequired for each change in the type of workpiece can be reduced.

What is claimed is:
 1. A guide rail mechanism for a bonding apparatusequipped with a pair of guide rails that guide a workpiece, wherein eachof said guide rails consists of:an edge surface guide rail element whichis provided on a guide rail stand and guides an edge surface of saidworkpiece, and an undersurface guide rail element which is disposedbeneath said edge surface guide rail element and supports anundersurface of an edge portion of said workpiece; and said mechanismfurther comprises an undersurface guide rail element driving means whichraises and lowers said undersurface guide rail element.
 2. A guide railmechanism for a bonding apparatus according to claim 1, wherein saidundersurface guide rail element driving means comprises:a rotationalshaft consisting of a shaft portion, which is rotatably installed insaid guide rail stand, and a cam portion, which is provided at one endof said shaft portion and supports, raises and lowers said undersurfaceguide rail element; and a rotational driving means which rotates saidrotational shaft.
 3. A guide rail mechanism for a bonding apparatusaccording to claim 1, wherein said undersurface guide rail elementdriving means comprises:a rotational shaft consisting of a shaftportion, which is rotatably installed in said guide rail stand, and acam portion, which is provided at one end of said shaft portion andsupports, raises and lowers said undersurface guide rail element; arotational driving means which rotates said rotational shaft; and acontrol device which controls an amount of driving of said rotationaldriving means.
 4. A guide rail mechanism for a bonding apparatusaccording to claim 1, wherein said undersurface guide rail elementdriving means comprises:a rotational shaft consisting of a shaftportion, which is rotatably installed in said guide rail stand, and acam portion, which is provided at one end of said shaft portion andsupports, raises and lowers said undersurface guide rail element; and arotational shaft positioning means which holds said rotational shaft ina plurality of stopping positions.
 5. A guide rail mechanism for abonding apparatus equipped with a pair of guide rails that guide aworkpiece, wherein each of said guide rails consists of:an edge surfaceguide rail element which is provided on a guide rail stand and guides anedge surface of said workpiece, a top of a guide section thereof beingopen, and an undersurface guide rail element which is disposed beneathsaid edge surface guide rail element and supports an undersurface of anedge portion of said workpiece; and said mechanism further comprises anundersurface guide rail element driving means which raises and lowerssaid undersurface guide rail element.
 6. A guide rail mechanism for abonding apparatus comprising:a pair of guide rails for guiding aworkpiece to be conveyed, each of said pair of guide rails consisting ofan edge surface guide rail element, which is provided on a guide railstand and guides an edge surface of said workpiece, and an undersurfaceguide rail element, which is disposed beneath said edge surface guiderail element and supports an undersurface of an edge portion of saidworkpiece; and an undersurface guide rail element driving means whichmoves said undersurface guide rail element toward and away from saidedge surface guide rail element so as to change a distance between saidedge surface guide rail element and said undersurface guide rail elementfor workpieces of different thicknesses.